Control
Management methods and protocols supported by the switch.
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SSH. Abbreviation for Secure Shell, i.e. "Safe shell". The SSH protocol provides a fairly high degree of security, because. encrypts all transmitted data, including passwords. Suitable for managing almost all major network protocols, but requires a special utility on the host computer.
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Telnet. A network management protocol that provides configuration using a text-based command line. It does not use encryption and does not protect transmitted data, and is also devoid of a graphical interface, which is why in many areas it has been supplanted by more secure (SSH) or more convenient (web interface) options. However, it is still used in modern network equipment.
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Web interface. This function allows you to open the management interface of the switch in a common Internet browser. The main convenience of the web interface is that it does not require additional software — a browser is enough (and it is available in any "self-respecting" modern OS). Thus, knowing the device address, login and password, you can manage the settings from almost any computer on the network (unless, of course, otherwise specified in the access parameters).
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SNMP. Abbreviation for Simple Network Management Protocol, i.e. "simple network control protocol". It is a stan
...dard part of the common TCP/IP protocol on which both the Internet and many local networks are built. It uses two types of software — "managers" on control computers and "agents" on managed computers (in this case, on a router). The degree of security is relatively low, but SNMP can be used for simple management tasks.
Note that this list is not exhaustive — modern switches may provide other management options, for example, support for proprietary utilities and special technologies from the same manufacturer.Standards
Static routing is carried out according to the standard scheme, but different protocols are used for dynamic routing. The idea of dynamic is that the route table is constantly edited programmatically, in automatic mode. To do this, network devices (more precisely, routing programs running on them) exchange service information with each other, on the basis of which optimal addresses are written to the table. One of the fundamental concepts of dynamic routing is a
metric — a complex indicator that determines the conditional distance to a specific address (in other words, how close this or that route is to the optimal one). Different protocols use different ways to define and share metrics; here are some of the most common options:
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R.I.P. One of the most widely used dynamic routing protocols; was first applied back in 1969 on the ARPANET, which became the forerunner of the modern Internet. Refers to the so-called distance-vector algorithms: the metric in the RIP protocol is indicated by the distance vector between the router and the network node, and each such vector includes information about the direction of data transfer and the number of "hops" (sections between intermediate nodes) to the corresponding network device. When using RIP, metrics are sent over the network every 30 seconds; at the same time, having received from the "neighbor" data about the nodes known to it, the router makes a number of clarifications and add
...itions to this data (in particular, information about itself and about directly connected network devices) and transmits further. After receiving up-to-date data throughout the network, the router selects for each individual node the shortest route from several received alternatives and writes it into the routing table.
The advantages of the RIP protocol include ease of implementation and undemanding. On the other hand, it is poorly suited for large networks: the maximum number of hops in RIP is limited to 15, and the complication of the topology leads to a significant increase in service traffic and the load on the computing part of the equipment — as a result, the actual network performance decreases. Thus, more advanced protocols such as (E)IGRP and OSPF (see below) have become more common for professional applications.
— IGRP. A proprietary routing protocol created by Cisco for autonomous systems (in other words, local networks with a single routing policy with the Internet). Also, like RIP (see above), it refers to distance vector protocols, however, it uses a much more complicated procedure for determining the metric: it takes into account not only the number of hops, but also delay, throughput, actual network congestion, etc. In addition, the protocol implements a number of specific mechanisms to improve communication reliability. Due to this, IGRP is well suited even for fairly complex networks with an extensive topology.
— EIGRP. An improved and modernized successor to the IGRP protocol described above, developed by the same Cisco. Created as an alternative to OSPF (see below), it combines the properties of distance vector protocols and standards with link state tracking. One of the main advantages over the original IGRP was the improvement in the algorithm for disseminating data about changes in the topology in the network, due to which the probability of looping (characteristic of all distance vector standards) was reduced to almost zero. And among the differences between this protocol and OSPF, higher performance and a more advanced algorithm for calculating the metrics are claimed with less configuration complexity and resource requirements.
OSPF. An open autonomous system routing protocol created by the IETF (Internet Design Council) and first implemented in 1988. Refers to protocols with link state tracking, uses the so-called Dijkstra algorithm (algorithm for finding the shortest paths) to build routes. The OSPF routing process is as follows. Initially, the router communicates with similar devices, establishing a "neighbor relationship"; neighbors are routers within the same autonomous zone. Then the neighbors exchange metrics among themselves, synchronizing the data, and after such synchronization, all routers receive a complete database of the state of all links in the network (LSDB). Already on the basis of this base, each of these devices builds its own route table using Dijkstra's algorithm. The main advantages of OSPF are high speed (speed of convergence), a high degree of optimization of the use of channels and the ability to work with network masks of variable length (which, in particular, is especially convenient with a limited resource of IP addresses). The disadvantages include the exactingness of the computing resources of routers, a significant increase in load with numerous such devices in the network, and the need to complicate the topology in large networks, dividing such networks into separate zones (area). In addition, OSPF does not have clear criteria for determining the metric: the “cost” of each hop can be calculated according to different parameters, depending on the switch manufacturer and the settings chosen by the administrator. This expands the possibilities for configuring routing and at the same time greatly complicates this procedure.
Modern switches may provide other routing protocols in addition to those described above.Operating temperature
The range of operating temperatures allowed for the switch, in other words, the air temperature at which the device is guaranteed to remain operational.
All modern switches are able to normally endure conditions that are comfortable for a person. Therefore, you should pay attention to this indicator, first of all, in cases where the conditions at the installation site of the switch will differ markedly from home / office; a typical example is the placement of ISP equipment in the attic of a multi-storey building. At the same time, special attention should be paid to the lower limit of the temperature range — not every device is able to operate at sub-zero temperatures. If we talk about specific numbers, then for an unheated room frost resistance is desirable at least at the level of
-5 °C, and ideally —
— 20 °C(although, of course, this also depends on the climate).
Also note that, in addition to temperature, most switches have restrictions on the relative humidity of the air; these restrictions are usually specified in the documentation.
